4.1 Ecosystems: Everything Is Connected 4.2 Evolution 4.3 The
Diversity of Living Things
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Classroom Catalyst
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4.1 Ecosystems: Everything is Connected Objectives Distinguish
between the biotic and abiotic factors in an ecosystem. Describe
how a population differs from a species. Explain how habitats are
important for organisms.
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Defining an Ecosystem Ecosystems are communities of organisms
and their abiotic environment. Examples are an oak forest or a
coral reef. Ecosystems do not have clear boundaries. Things move
from one ecosystem to another. Pollen can blow from a forest into a
field, soil can wash from a mountain into a lake, and birds migrate
from state to state.
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Organization in an Ecosystem
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In order to survive, ecosystems need certain basic components:
energy, mineral nutrients, water, oxygen, and living organisms.
Plants and rocks are components of the land ecosystems, while most
of the energy of an ecosystem comes from the sun. If one part of
the ecosystem is destroyed or changes, the entire system will be
affected. The Components of an Ecosystem
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Biotic and Abiotic Factors Biotic factors are environmental
factors that are associated with or result from the activities of
living organisms which includes plants, animals, dead organisms,
and the waste products of organisms. Abiotic factors are
environmental factors that are not associated with the activities
of living organisms which includes air, water, rocks, and
temperature. Scientists can organize these living and nonliving
things into various levels.
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Organisms Organisms are living things that can carry out life
processes independently. You are an organism, as is an ant, and ivy
plant, and each of the many bacteria living in your intestines.
Every organism is a member of a species. Species are groups of
organisms that are closely related can mate to produce fertile
offspring.
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Populations Members of a species may not all live in the same
place. Field mice in Maine will not interact with field mice in
Texas. However, each organism lives as part of a population.
Populations are groups of organisms of the same species that live
in a specific geographical area and interbreed. For example, all
the field mice in a corn field make up a population of field
mice.
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Populations An important characteristic of a population is that
its members usually breed with one another rather than with members
of other populations For example, bison will usually mate with
another member of the same herd, just as wildflowers will usually
be pollinated by other flowers in the same field.
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Communities Communities are groups of various species that live
in the same habitat and interact with each other. Every population
is part of a community. The most obvious difference between
communities is the types of species they have. Land communities are
often dominated by a few species of plants. These plants then
determine what other organisms can live in that community.
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Habitat Habitats are places where an organism usually lives.
Every habitat has specific characteristics that the organisms that
live there need to survive. If any of these factors change, the
habitat changes. Organisms tend to be very well suited to their
natural habitats. If fact, animals and plants usually cannot
survive for long periods of time away from their natural
habitat.
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4.1 Section Review Questions 1. Describe a population not
mentioned in this section. 2. Describe which factors of an
ecosystem are not part of a community 3. Explain the difference
between a population and a species.
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4.2 Evolution Objectives Explain the process of evolution by
natural selection. Explain the concept of adaptation. Describe the
steps by which a population of insects becomes resistant to
pesticide.
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Evolution by Natural Selection English naturalist Charles
Darwin observed that organisms in a population differ slightly from
each other in form, function, and behavior. Some of these
differences are hereditary. Darwin proposed that the environment
exerts a strong influence over which individuals survive to produce
offspring, and that some individuals, because of certain traits,
are more likely to survive and reproduce than other
individuals.
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Evolution by Natural Selection Natural selection is the process
by which individuals that have favorable variations and are better
adapted to their environment survive and reproduce more
successfully than less well adapted individuals do. Darwin proposed
that over many generations, natural selection causes the
characteristics of populations to change. Evolution is a change in
the characteristics of a population from one generation to the
next.
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Nature Selects Darwin thought that nature selects for certain
traits, such as sharper claws, because organisms with these traits
are more likely to survive. Over time, the population includes a
greater and greater proportion of organisms with the beneficial
trait. As the populations of a given species change, so does the
species.
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Evolution by Natural Evolution
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Nature Selects An example of evolution is a population of deer
that became isolated in a cold area. Some of the deer had genes for
thicker, warmer fur. These deer were more likely to survive, and
their young with thick fur were more likely to survive to
reproduce. Adaptation is the process of becoming adapted to an
environment. It is an anatomical, physiological, or behavioral
change that improves a populations ability to survive.
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Coevolution The process of two species evolving in response to
long-term interactions with each other is called coevolution. An
example is the Hawaiian honeycreeper, which has a long, curved beak
to reach nectar at the base of a flower. The flower has structures
that ensure that the bird gets some pollen on its head. When the
bird moves the next flower, some of the pollen will be transferred,
helping it to reproduce.
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Nature Selects
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Coevolution The honeycreepers adaptation is along, curved beak.
The plant has two adaptations: The first is the sweet nectar, which
attracts the birds. The second is the flower structure that forces
pollen onto the birds head when the bird sips nectar.
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Evolution by Artificial Selection Artificial selection is the
selective breeding of organisms, by humans, for specific desirable
characteristics. Dogs have been bred for certain characteristics.
Fruits, grains, and vegetables are also produced by artificial
selection. Humans save seeds from the largest, and sweetest fruits.
By selecting for these traits, farmers direct the evolution of crop
plants to produce larger, sweeter fruit.
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Evolution of Resistance Resistance is the ability of an
organism to tolerate a chemical or disease-causing agent. An
organism may be resistant to a chemical when it contains a gene
that allows it to break down a chemical into harmless substances.
Humans promote the evolution of resistant populations by trying to
control pests and bacteria with chemicals.
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Pesticide Resistance A pesticide sprayed on corn to kill
grasshoppers, for example, may kill most of the grasshoppers, but
those that survive happen to have a gene that protects them from
the pesticide. These surviving insects pass on this resistant gene
to their offspring. Each time the corn is sprayed, more resistant
grasshoppers enter the population. Eventually the entire population
will be resistant, making the pesticide useless.
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Pesticide Resistance
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4.2 Section Review Questions 1. Explain what an adaptation is,
and provide three examples. 2. Explain the process of evolution by
natural selection. 3. Describe one way in which artificial
selection can benefit humans. 4. Explain how a population of
insects could become resistant to a pesticide.
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4.3 The Diversity of Living Things Objectives Name the three
domains and four kingdoms of organisms and list characteristics of
each. Explain the importance of bacteria and fungi in the
environment. Describe the role of protists in the ocean
environment. Describe how organisms interact and depend on each
other for survival.
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The Diversity of Living Things Most scientists classify
organisms into three domains and four kingdoms based on different
characteristics. Members of the three domains get their food in
different ways and are made up of different types of cells, the
smallest unit of biological organization. The cells of animals,
plants, fungi, and protists all contain a nucleus. While cells of
bacteria, fungi, and plants all have cell walls.
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Levels of Classification
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Archaea and Bacteria Archaea differ from bacteria in their
genetics and the makeup of their cell wall. Bacteria are
microscopic, unicellular organisms that usually have a cell wall
and reproduce by cell division. Unlike all other organisms,
bacteria and archaea lack nuclei. Bacteria and archaea live in
every habitat on Earth, from hot springs to the bodies of
animals.
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Bacteria and the Environment Some kinds of bacteria break down
the remains and wastes of other organisms and return the nutrients
to the soil. Others recycle nutrients, such as nitrogen and
phosphorus. Certain bacteria can convert nitrogen from the air into
a form that plants can use. This conversion is important because
nitrogen is the main component of proteins and genetic
material.
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Bacteria and the Environment Bacteria also allow many
organisms, including humans, to extract certain nutrients from
their food. The bacterium, Escherichia coli or E. coli, is found in
the intestines of humans and other animals and helps digest food
and release vitamins that humans need.
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Fungi A fungus is an organism whose cells have nuclei, rigid
cell walls, and no chlorophyll and that belongs to the kingdom
Fungi. Cell walls act like mini-skeletons that allow fungi to stand
up right. A mushroom is the reproductive structure of a fungus. The
rest of the fungus is an underground network of fibers that absorb
food from decaying organisms in the soil.
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Fungi Fungi get their food by releasing chemicals that help
break down organic matter, and then absorbing the nutrients. The
bodies of most fungi are huge networks of threads that grow through
the soil, dead wood, or other material on which the fungus is
feeding. Like bacteria, fungi play an important role in breaking
down the bodies of dead organisms.
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Fungi Some fungi, like some bacteria, cause disease. Athletes
foot is an example of a condition caused by fungi. Other fungi add
flavor to food as in blue cheese. The fungus gives the cheese both
its blue color and strong flavor. Yeasts are fungi that produce the
gas that makes bread rise.
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Protists Protists are diverse organisms that belong to the
kingdom Protista. Some, like amoebas, are animal-like. Others are
plantlike, such as kelp, and some resemble fungi. Most protists are
unicellular, microscopic organisms, including diatoms, which float
on the ocean surface. Another protist, Plasmodium, is the
unicellular organism that causes the disease malaria.
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Protists From an environmental standpoint, the most important
protists are algae. Algae are plantlike protists that can make
their own food using light energy from the sun. They range in size
from the giant kelp to the unicellular phytoplankton, which are the
initial source of food in most ocean and freshwater
ecosystems.
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Plants Plants are multicellular organisms that make their own
food using light energy from the sun and have cell walls. Most
plants live on land where they use their leaves to get sunlight,
oxygen, and carbon dioxide from the air. While absorbing nutrients
and water from the soil using their roots. Leaves and roots are
connected by vascular tissue, which has thick cell walls and serves
is system of tubes that carries water and food.
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Plants Plants with no vascular tissue are called nonvascular
plants. Nonvascular plants lack specialized conducting tissues,
roots, stems, and leaves, so water must move from the environment
throughout the plant. Nonvascular plants such as mosses, live in
damp places.
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Gymnosperms Gymnosperms are woody vascular seed plants whose
seeds are not enclosed by an ovary or fruit. Conifers, such as pine
trees, are gymnosperms that bear cones. Much of our lumber and
paper comes from gymnosperms.
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Gymnosperms Gymnosperms have several adaptations that allow
them to live in dry conditions. They can produce pollen, which
protects and moves sperm between plants. These plants also produce
seeds, which protect developing plants from drying out. A conifers
needle-like leaves also lose little water.
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Angiosperms Angiosperms are flowering plants that produce seeds
within fruit. Most land plants are angiosperms. The flower is the
reproductive structure of the plant. Some angiosperms, like
grasses, have small flowers, that use wind to disperse their
pollen. Other angiosperms have large flowers to attract insects and
birds. Many flowering plants depend on animals to disperse their
seeds and carry their pollen.
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Angiosperms Most land animals are dependent on flowering
plants. Most of the food we eat, such as wheat, rice, beans,
oranges, and lettuce comes from flowering plants. Building
materials and fibers, such as oak and cotton, also come from
flowering plants.
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Animals Animals cannot make their own food. They must take it
in from the environment. Animal cells have no cell walls, so their
bodies are soft and flexible. Although, some animals have evolved
hard skeletons against which their muscles can pull to move their
bodies. As a result, animals are much more mobile than plants. All
animals move around in their environment during at least one stage
in their lives.
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Invertebrates Invertebrates are animals that do not have
backbones. Many live attached to hard surfaces in the ocean and
filter their food out of the water, such as corals, various worms,
and mollusks. These organisms are only mobile when they are larvae.
At this early stage in their life they are part of the oceans
plankton.
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Invertebrates Other invertebrates, including squid in the ocean
and insects on land, actively move in search of food. More insects
exist on Earth than any other type of animal. Insects are
successful for many reasons: they have a waterproof external
skeleton, can move and reproduce quickly, most insects can fly, and
their small size allows them to live on little food and to hide
from enemies in small places.
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Invertebrates Many insects and plants have evolved together and
depend on each other to survive. Insects carry pollen from male
fruit parts to fertilize a plants egg, which develops into fruits
such as tomatoes, cucumbers, and apples. Insects are also valuable
because they eat other insects that we consider to be pests.
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Invertebrates However, insects and humans are often enemies.
Bloodsucking insects transmit human diseases such as malaria,
sleeping sickness, and West Nile virus. Insects do most damage
indirectly by eating our crops.
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Vertebrates Vertebrates are animals that have a backbone, and
includes mammals, birds, reptiles, amphibians, and fish. The first
vertebrates were fish, but today most vertebrates live on land. The
first land vertebrates were reptiles. These animals were successful
because they have an almost waterproof egg which allows the egg to
hatch on land, away from predators in the water.
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Vertebrates Birds are warm-blooded vertebrates with feathers.
They keep their hard-shelled eggs and young warm until they have
developed insulating layers of fat and feathers. Mammals are
warm-blooded vertebrates that have fur and feed their young milk.
Birds and mammals have the ability to maintain a high body
temperature which allows them to live in cold areas, where other
animals cannot live.
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4.3 Section Review Questions 1. Describe how animals and
angiosperms depend on each other. Write a short paragraph to
explain your answer. 2. Describe the importance of protists in the
ocean. 3. Name the four kingdoms of life, and give two
characteristics of each. 4. Explain the importance of bacteria and
fungi in the environment.